Conductive doped metal-glass compositions and methods

Abstract

Provided herein are conductive glass-metal compositions, as well as methods of making and using such compositions. In one example, the compositions include gold (Au) doped lithium-borate glasses shown to exhibit a transition from ionic to electronic conduction within the same sample. This is achieved via appropriate heat treatment, and particularly by heat treatment after annealing, wherein the post-annealing heat treatment is performed at temperatures below the glass transition temperature (T g ). The methods described herein are believed to introducing polarons formed from the trapping of electrons at partially ionized gold atoms. This unique electrical response provides new functionality to this class of nanocomposites. Additionally, increased thermal conductivity can be provided to an otherwise low conductive glass composition using the inventive methods and other subject matter provided herein.

The invention claimed is: 
     
       1. A method for producing an electrically conductive glass, the method comprising the steps of:
 providing a base composition comprising a lithium carbonate powder, and a boric acid powder; 
 adding to the base composition at least one metal salt; 
 mixing the base composition and metal salt to form a doped base composition; 
 melting the doped base composition to form a doped glass melt; 
 casting the doped glass melt at approximately room temperature to yield a doped glass article; 
 thereafter, thermally conditioning the doped glass article at a temperature of approximately the glass transition temperature (Tg) to remove residual stress; 
 after the step of thermally conditioning the doped glass article, heat treating the doped glass article at a temperature below Tg for a time sufficient to yield a doped glass product having electrically conductive metal particles that are substantially homogeneously dispersed throughout the doped glass product, the doped glass product having an electrical conductivity of at least one order of magnitude greater than the electrical conductivity of a non-doped glass article made by the steps of melting the base composition without adding a metal salt, casting, thermally conditioning, and heat treating. 
 
     
     
       2. The method according to  claim 1 , wherein the amount of metal salt provided is between about 0.02 and 0.20 mole percent. 
     
     
       3. The method according to  claim 1 , wherein the metal salt comprises at least one of a metal selected from the group consisting of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Zn, Cd, and Hg. 
     
     
       4. The method according to  claim 3 , wherein the temperature below Tg is a temperature of at least 30 degrees Celsius below Tg, and wherein the time sufficient to yield the doped glass product is at least about two hours. 
     
     
       5. The method according to  claim 3 , wherein the doped glass product comprises metal particles having a mean diameter of between about 1×10 1  to 1×10 2  nanometers. 
     
     
       6. The method according to  claim 3 , wherein the metal salt is HAuCl 4 .3H 2 O. 
     
     
       7. The method according to  claim 6 , wherein the doped glass product comprises metal particles having a mean diameter of between about 1×10 1  to 1×10 2  nanometers. 
     
     
       8. The method according to  claim 4 , wherein the metal salt is HAuCl 4 .3H 2 O. 
     
     
       9. The method according to  claim 8 , wherein the metal particles in the doped glass product average between about 100 nm to about 300 nm in size. 
     
     
       10. The method, according to  claim 1 , wherein the doped glass product exhibits an observed activation energy of about 0.34 eV, which is characteristic of polaron conduction. 
     
     
       11. The method according to  claim 1 , wherein the distance between the metal particles in the doped glass product is greater than about 1 micrometer. 
     
     
       12. The method according to  claim 3 , wherein the doped glass product exhibits an observed activation energy of about 1.00 eV, which is characteristic of ionic conduction. 
     
     
       13. The method according to  claim 10 , wherein the doped glass product comprises electrically conductive metal particles spaced apart by an average distance greater than about 1 micrometer. 
     
     
       14. The method according to  claim 13 , wherein the distance between the electrically conductive metal particles are spaced apart by an average distance less than about 1 micrometer. 
     
     
       15. A method for producing an electrically conductive glass, the method comprising the steps of:
 providing a base composition comprising a lithium carbonate powder, and a boric acid powder; 
 adding to the base composition at least one metal salt comprising at least one metal selected from the group consisting of Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, and Hg; 
 mixing the base composition and metal salt to form a doped base composition; 
 melting the doped base composition to form a doped glass melt; 
 casting the doped glass melt at approximately room temperature to yield a doped glass article; 
 thereafter, thermally conditioning the doped glass article at a temperature of approximately the glass transition temperature (Tg) to remove residual stress; 
 after the step of thermally conditioning the doped glass article, heat treating the doped glass article at a temperature below Tg for a time sufficient to yield a doped glass product having electrically conductive metal particles that are substantially homogeneously dispersed throughout the doped glass product, the doped glass product having an electrical conductivity that exhibits an activation energy of between about 0.34 eV and about 1.0 eV. 
 
     
     
       16. The method according to  claim 2 , wherein the amount of metal salt provided is between about 0.02 and 0.20 mole percent. 
     
     
       17. The method according to  claim 15 , wherein the temperature below Tg is a temperature of at least 30 degrees Celsius below Tg, and wherein the time sufficient to yield the doped glass product is at least about two hours. 
     
     
       18. The method according to  claim 15 , wherein the doped glass product comprises metal particles having a mean diameter of between about 1×10 1  to 1×10 2  nanometers. 
     
     
       19. The method according to  claim 15 , wherein the metal salt is HAuCl 4 .3H 2 O. 
     
     
       20. The method of  claim 15 , wherein the doped glass product is a doped glass substrate.